Civil Air Patrol rocks. Don't join any program just because you think it might increase your shots at getting into a SA/SMC; join it because you've done your research and you like what you're seeing. Asking these questions is an excellent first step.
I received some top notch leadership training from CAP. Just as an example, the national Cadet Officer School is held each summer at Maxwell AFB. COS is about 10 days long. It's modeled off the USAF Squadron Officer School, which is the professional development course all USAF Captains (LTs) are required to attend before they're promotable to Major (LCDR). CAP cadets receive a bite-size version of the same training USAF Capts do, taught by many of the same instructors. When I attended the Civic Leadership Academy, I toured the Pentagon, toured the CIA, met the Deputy Secretary of State, had lunch with an Ambassador, met my congressmen, and toured the Supreme Court. This year's CLA actually met Justice Scalia, who randomly decided when he met the CAP cadets to rearrange his own schedule to give them an hour-long, closed door Q&A session. When I went on the International Air Cadet Exchange, I spent a week and a half touring Turkey, learning about the Turkish Air Force and aviation industry. I had dinner with the retired Turkish one-star general who was then serving as the chief of aviation (military and civil) within the Turkish government.
I've known a few Sea Cadets. While I'm no expert in their programs, I know they provide the opportunity to spend a few weeks aboard ship with the Navy and/or the Coast Guard. They also have an activity designed to introduce you to life as a member of a Seal Team. I think they also have courses for amphibious training and firefighting, and I'm certain they provide top notch leadership academies, as well.
But don't forget the Young Marines and the US Army Cadet Corps.
I wanted to join the Young Marines, with the USNSCC as a second choice. The closest units for each were a 45 minute drive one way. I found a CAP squadron 15 minutes away. It was a matter of convenience for my family, but I am so grateful for the opportunities and experiences CAP gave me. Talk to a Sea Cadet, and I'm sure they'll share equally awesome experiences with you that they never could have had if they'd joined CAP, instead.
That said... I'm pretty sure that nobody else from the squadron I initially joined went to COS, CLA, or the International Air Cadet Exchange, and I know no one else served in the leadership roles I was fortunate enough to learn from for other summer training activities. Once I joined, I had to seek information, figure out the paperwork and do things for myself. I learned a lot about taking initiative and being responsible for reaching my own goals.
Regardless of whether or not joining a specific cadet program will help you get into USNA or any other college you're applying to, you'll become a better person and a better leader. But they probably won't care very much if you only got promoted once and never did anything outside of weekly meetings.
Here's my point: There are some awesome, awesome opportunities out there in the way of military-style cadet programs for high school students. Part of what makes them awesome is that you have to take some initiative and seek these opportunities out yourself, which is kind of like real life.
Figure out which cadet program works best for you, and then never look back.
Good luck,
Jackie M. Briski
VMI Class of 2009
Capt, CAP